1762-41-0Relevant articles and documents
Strongly blue luminescent cationic iridium(III) complexes with an electron-rich ancillary ligand: Evaluation of their optoelectronic and electrochemiluminescence properties
Ladouceur, Sebastien,Swanick, Kalen N.,Gallagher-Duval, Shawn,Ding, Zhifeng,Zysman-Colman, Eli
, p. 5329 - 5343 (2013)
Two strongly blue luminescent cationic heteroleptic iridium complexes 1b and 2b bearing a 4,4′-bis(dimethylamino)-2,2′-bipyridine (dmabpy) ancillary ligand and either 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (dFphtl) or 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppyH), respectively, have been synthesized and fully characterized. In comparison with other analogues, the interplay of the triazole unit with the dmabpy unit and methylation of the pyridine ring are discussed with respect to the photophysical, electrochemical, and electrochemiluminescent (ECL) properties of the complexes. The two complexes, 1b and 2b, are blue emitters with λmax = 495 and 494 nm, respectively. The nature of the excited states was established by various photophysical and photochemical experiments as well as DFT calculations. Both complexes emit from a ligand-centered state, however, the emission of 1b possesses significant charge-transfer character, which is absent in 2b. The presence of the methyl group on the cyclometalating ligand leads only to a modest increase in the radiative rate constant, k r, but otherwise does not appreciably influence the optoelectronic properties of the complex compared with the non-methylated analogue. In contrast, the efficacy of the ECL emission when scanning to 2.50 V is strongly influenced by the presence of the methyl group. ECL emission is also enhanced in complexes bearing dmabpy ancillary ligands compared with those containing dtBubpy ligands. The two complexes exhibit similar electrochemical behavior. Incorporation of the dmabpy ligand shifts both the oxidation and reduction cathodically. The combination of the dmabpy and dFphtl groups increases the redox potential difference and thus the HOMO-LUMO gap but the emission is not further blueshifted. Thus, the structural modification of the cyclometalating ligand, although only modestly tuning the emission energy, modulates the nature of the excited state and the efficiency of the ECL process. The synthesis, photophysical, electrochemical, and electrochemiluminescent properties of two highly emissive cationic blue-emitting Ir complexes are reported. Variation of the ligand results in a change in the nature of the emission. The decoration on both the cyclometalating and ancillary ligands strongly influences the ECL efficiencies. A detailed DFT/TDDFT study corroborates experiment. Copyright
Novel di- and tetra(pyrazolyl)bipyridine ligands and their Co (II)-complexes for electrochemical applications
Zavozin, Alexander G.,Simirskaya, Nina I.,Nelyubina, Yulia V.,Zlotin, Sergei G.
, p. 7552 - 7556 (2016)
Novel di- and tetra(pyrazolyl)bipyridine ligands have been prepared from available bipyridine N-oxide and N,N′-dioxide nitro derivatives via nucleophilic substitution reactions. The ligands were converted to the corresponding homoleptic octahedral cobalt
Electronic effects on reactivity and anticancer activity by half-sandwich N,N-chelated iridium(iii) complexes
Guo, Lihua,Zhang, Hairong,Tian, Meng,Tian, Zhenzhen,Xu, Yanjian,Yang, Yuliang,Peng, Hongwei,Liu, Peng,Liu, Zhe
supporting information, p. 16183 - 16192 (2018/10/04)
The synthesis and characterization of a series of organometallic half-sandwich N,N-chelated iridium(iii) complexes bearing a range of electron-donating and withdrawing substituents were described. The X-ray crystal structures of complexes 1, 3 and 5 have been determined. This work demonstrated how the aqueous chemistry, catalytic activity in converting coenzyme NADH to NAD+ and anticancer activity can be controlled and fine-tuned by the modification of the ligand electronic perturbations. In general, the introduction of an electron-withdrawing group (-Cl and-NO2) on the bipyridine ring resulted in increased anticancer activity, whereas an electron-donating group (-NH2,-OH and-OCH3) decreased the anticancer activity. Complex 6 bearing a strongly electron-withdrawing NO2 group displayed the highest anticancer activity (7.3 ± 1.2 μM), ca. three times as active as cisplatin in the A549 cell line. Notably, selective cytotoxicity for cancer cells over normal cells was observed for complexes 1 and 6. DNA binding does not seem to be the primary mechanism for cancer fighting. However, the aqueous chemistry, cell apoptosis and cell cycle, which show similar dependence on the ligand electronic perturbations as the anticancer activity, appear to together contribute to the anticancer potency of theses complexes. This work may provide an alternative strategy to enhance anticancer activity for these N,N-chelated organometallic half-sandwich iridium(iii) complexes.
